2.2 Coastal ecosystems Flashcards
What are the 4 different coastal ecosystems?
Coral reef - Made up of large coral structures that join together to form a reef. Coral are composed of calcium carbonate
Mangrove - Salt tolerant trees that grow in coastal zones of tropical areas and tidal estuaries with muddy waters that are ruch in nutriesnt due to decaing leaves. Predominantly made up of mangrove trees which have stilt like roots
Sand dune - Mounds of sand create on coasts due to prevailing winds and contain halophytic and xerophytic vegetation
Salt marsh - Low lying coast wetlands, which are flooded and drained by saltwater brought in by the tides. They are very productive and fertile ecosystems
What conditions do they thrive in?
Coral Reefs:
- pH of around 7
- Temperature of 18 - 33oC
- They need light (generally form around 60 m depth)
- Clean water
- Salinity of 30-38 ppt
E.g. Great barrier reef
Mangroves:
- Sea surface temperature of more than 24oC in the warmest month
- Annual rainfall of at least 1250mm
- Found on estuaries that supply sufficeint sediment to support fertile growth
E.g. Amazon and Padma for Sunderbands
Sand Dunes:
- Common in areas with where there is prevailing onshore wind
- Large supply of sand
- Large tidal range
E.g. Studland beach
Salt Marshes:
- Form in sheltered bays, estuaries, and along the landward side of spits and islands and low energy environments
E.g. Rye harbour nature reserve
Global distribution of the ecosystems
Coral Reefs:
Near the equator and in the tropics. They are predominantly in the pacific and indian oceans. This is due to high ocean temperatures and levels of sunlight
Mangroves:
In the tropics becuase of high levels or rainfall and consistent high temerpatures and they are always found on coastlines on major continents. This is because of higher temperatures and access to minerals from rivers. Mangroves cover 25% of the worlds tropical coastline and the largest existing example is sunderbans which border india and bangladesh.
Sand Dunes:
Found in arid conditions at all latitudes with prevailing onshroe wind and large supply of sand
Salt marshes:
Most common in temperate zones in middle to high latitudes
Abiotic and Biotic characteristics of Mangroves
In a mangrove ecosystem, the interaction between mangrove trees (biotic) and saltwater (abiotic) is a crucial example of how these elements work together. Mangrove trees are specially adapted to survive in the saline waters of coastal regions, using specialized roots and salt-excreting glands to filter and manage excess salt. This adaptation not only allows the trees to thrive in challenging conditions but also helps stabilize the coastline by preventing soil erosion. In turn, the mangrove trees provide habitat and food for a wide range of species, such as crabs, fish, and birds, fostering a diverse ecosystem. This interaction demonstrates the intricate relationship between living organisms and their physical environment in maintaining ecological balance.
Another example of biotic and abiotic factors working together in harmony is mangrove trees (biotic) and rough water (abiotic) since the mangrove tree roots absorb the energy from strong currents and waves which provides a nursery for lemon sharks (biotic) to raise their young. Additionally mangrove trees need to have water constantly surrounding them for them to thrive
Nutrient cycle:
- Leaves from mangrove trees fall down into the water where crabs graze on it.
- Fungi and bacteria also break down the litter and prawns and fish feed on decomposed litter.
- Small particles of organic matter feeds smaller crustaceans which larger fish feed on.
- The remaining organic matter is absorbed back into the mangrove roots
What are the key features of these coastal ecosystems?
Coral Reefs:
There are 3 different types of reefs:
- Fringing reefs: Reefs that fringe the coast of a landmass
- Barrier reefs: Reefs occur at a grater distance from the shore barrier, reefs tend to be broader and older
- Atoll reefs: Similar to barrier reefs but the difference is atoll flank oceanic islands but barrier can flank continents
- 25% of the words fish breed, grow and live in coral reefs
Mangroves:
- One hectare in the philippines can yield 400 kg of fish and 75 kg of shrimp annually
- Important breeding ground for species such as lemonshark
- Act as natural barriers to hurricanes and tropical storms
- Can also be natural filters for sewage and why coral reefs are often located near mangroves since mangroves clean the water.
Sand Dunes:
- Once marram grass and sea couch are established on the ebach, they reduce the wind speed and this helps trap fresh sand
- Dynamic environment as important changes take place in a very short amount of time.
- Extensive sandy beaches are almost always backed by sand dunes
Salt marshes:
- Provide many services, such as protection from coastal flooding and erosion, grazing for animals, and food, refuge and nurseries for many species.
All provide tourism
What are the threats to Coral reefs?
Mining - quarrying and dredging for the cement industry. This destroys the coral habitat
Boat propellers and anchors - Destroy coral habitat
Destructive fishing practices:
- Fishers use dynamite to flush out fish and cyanide solution to catch live fish
- Overfishing may reduce the number of grazing fish that keep coral clear of algae
Pollution - Plastics can block sunlight to algae which feeds corals. It can spread disease and cut into coral which make them more susceptible to disease
What are the threats to Mangroves?
Pollution of waterways can kill wildlife in mangroves since it is toxic.
Deforestation of mangroves for timber and making area for building damages mangrove forests and habitat destruction. When there are less mangrove trees to protect the current forest the mangroves are more vulnerable to damage from storm surges. It also means the filtering from mangroves is reduced which leaves surrounding corals to suffer from murky waters and inhibits their ability to survive.
Sea level rise - Mangroves may not be able to keep up with rising sea levels, which can lead to dieback. Record highs: In 2023, the global average sea level was 3.99 inches higher than it was in 1993. Rising in sea levels can weaken the root structure of mangroves.
Overfishing - some fo the food web is disrupted as certain species are removed or in significant decline - impacts those reliant on that species. This also means that plant tha fish eat are not going to be controlled causing wider issues.
What are the threats to Sand Dunes?
Mining for sand - Extracting sand destabilizes dunes which made them more at risk of wind + wave erosion as sand
Coastal development - the use of hard engineering such as groynes reduces available sediment for sand dunes further along the coast meaning that beaches get smaller and sand dunes cannot develop properly so they start to be eroded more easily.
Tourist - trampling of grasses and small plants can destabilise the dunes. If this happens then the dunes can be eroded by the wind.
What are the threats to Salt Marshes?
Many species within the salt marsh are sensitive to noise and disturbance, such as nesting birds. - Waterfront developments and tourists with dogs can create significant noise which stops birds species from effectively reproducing which threatens species survival in the area.
Coastal management such as groynes, at important sites of economic value further along the coast, can reduce the amount of sediment brought down by longshore drift to salt marshes. - This places the salt marsh at risk of erosion as the protective sediment layers in front of it are being removed by wave action.
